Although IQP-0410 possesses a favorable pharmacokinetic, safety pharmacology and toxicity profile, we believe that additional enhancement of biological activity is possible through additional development activities with lead molecules defined as the most active reverse transcriptase and virus entry inhibitors defined in our Phase I SBIR studies. Structure-activity relationship data obtained with the pyrimidinediones from our Phase I SBIR project indicates that a second generation pyrimidinedione may also be expected to meet and potentially exceed these necessary properties for a next generation NNRTI. A number of initial lead compounds with greater entry and RT inhibitory potential and stability have been identified for further development. Based on the results of our Phase I proposal as well as our experience with the development of our current clinical candidate pyrimidinedione IQP-0410, we intend to employ traditional medicinal chemistry to improve the solubility and stability of a new select pyrimidinedione, which will be defined according to parameters including antiviral activity, metabolism, and preformulation characteristics. Upon selection of our second generation pyrimidinedione inhibitor, we will employ formulation science to better deliver the potent, stable and more soluble pyrimidinedione to enhance bioavailability and pharmacokinetics. It is our expectation that this Phase II SBIR effort will yield a significant improvement in the therapeutic utility and potency of our next generation clinical candidate. PUBLIC HEALTH RELEVANCE: Although the currently approved NNRTIs (nevirapine, delavirdine, efavirenz and etravirine) are highly potent, significant improvements in therapeutic utility are still required. A new generation of NNRTIs must be developed which will allow once per day dosing, exhibit significantly reduced toxicity, be amenable to dosing in women of child bearing age, and possess a significantly higher genetic barrier to resistance selection. The primary goal of this proposal is to define and begin IND-directed development of a second generation pyrimidinedione clinical therapeutic candidate from among the highly active lead compounds defined during the course of our Phase I project. These selected lead pyrimidinediones have been prioritized based on their relative potential to inhibit both reverse transcription and virus entry and all are sub-nanomolar to low nanomolar concentration inhibitors of HIV-1. Detailed biological evaluation of these molecules will be combined with efforts to optimize the formulation and delivery of a new lead molecule, as well as the use of medicinal chemistry to improve the solubility, stability, and bioavailability of the selected compound. Comparative evaluation of compound metabolism and protein binding will also be utilized to help prioritize and define the next generation pryimidinedione clinical candidate possessing highly optimized pharmacokinetic properties and the highest possible potency against wild type, NNRTI-resistant and MDR viruses.